Method of forming a tapered container

ABSTRACT

A method of forming a tapered container, in which an impact extruded cylindrical container is used as a starting member. The bottom of the cylindrical container is domed upwardly, displacing the thickneed bottom edge of the container radially inwardly and forming a new bottom edge. The new bottom edge is then drawn upwardly to reduce the diameter of the container at its bottom, forming a tapered container.

mite States atent H91 Habash METHOD OF FORMHNG A TAPERED CONTAINER [75] Inventor: Michael B. Habash, Don Mills,

Ontario, Canada [73] Assignee: Advanced Extrusions Limited,

Penetang, Ontario, Canada [22] Filed: May 2, 1973 [21] Appl. No.: 356,437

[52] US. Cl. 113/120 M, 72/348 [51] lint. Cl B2ld 511/00 [58] Field of Search 72/347, 348, 367;

[56] References Cited UNITED STATES PATENTS 1,746,869 2/1930 Rosenthal 113/120 M [11] 33,14,040 ,1une41,1974

3,232,260 2/1966 Siemonsen .1 113/120 Primary Examiner-RiChard .1. Herbst Attorney, Agent, or Firm-Rogers, Breskin & Parr [57] ABSTRACT A method of forming a tapered container, in which an impact extruded cylindrical container is used as a starting member. The bottom of the cylindrical container is domed upwardly, displacing the thickneed bottom edge of the container radially inwardly and forming a new bottom edge. The new bottom edge is then drawn upwardly to reduce the diameter of the container at its bottom, forming a tapered container.

6 Claims, 10 Drawing 1 igures PATENTEDJUN 4:914

V l 2 f I I a I ........J

FIG. 3

FIG.

1 METHOD OF FORMING A TAPEREI) CONTAENIER This invention relates to a method of forming a tapered container.

Tapered containers are widely used for various purposes. For example, such containers are often used for the truncated conical centre section of annular cake and jelly molds (the tapered containers are welded or crimped to the remainder of the mold). in the past, such tapered containers have usually been made by spinning and drawing a flat plate to the required form, but this'method is relatively time consuming and expensive.

Accordingly, it is an object of the invention to provide a method of forming a tapered container in which a cylindrical container is used as a starting member, the cylindrical container then being tapered. Preferably, the cylindrical container is an impact extruded container, which can be formed quickly and inexpensively in large numbers.

In a preferred embodiment of the invention, the bottom of the cylindrical container is domed upwardly, to displacethe bottom edge of the container radially inwardly and to. form a new bottom edge. The new bottom edge is then drawn upwardly to reduce the diameter of the container at its bottom. This has a special ad vantage for impact extruded containers, because the bottom edge of such containers is normally thickened and cannot be drawn upwardly without creating a discontinuity in the wall of the resultant container.

Further objects and advantages of the invention will appear from the following description, taken together with the accompanying drawings, in which:

FIG. I is a side sectional view of a conventional prior art domed container;

FIG. 2 is a side sectional view showing an impact extruded container of the kind which the invention preferably uses as a starting member;

FIG. 3 is an enlarged view of a bottom edge portion of the container of FIG. 2;

FIG. 4 is a side sectional view showing a portion of the side wall of a tapered container that would be formed if the bottom edge portion shown in FIG. 3 were drawn upwardly;

FIG. 5 is a side sectional view showing the container of FIG 2 after its bottom has been domed;

FIG. s shows typical dies that may be used to dome the bottom of the FIG. 2 container;

FIG. 7 is a side sectional view showing typical dies used to taper the container of FIG. 5;

FIG. 8 is a diagrammatic view showing the manner in which the container of FIG. 5 is tapered;

FIG. 9 is a side sectional view showing alternative means for doming the bottom of the FIG. 2 container; and

FIG. 10 is a side sectional view showing a modification of the FIG. 9 embodiment.

Reference is first made to FIG. 1, which shows a typical tapered container 10 of the kind which it is the object of the invention to produce. The container 10 is a one piece container having a sidewall 12 which slopes at an angle A to the vertical. The angle A typically liesbetween about 5 and 12. The invention will produce tapered container of the kind shown in FIG. 1, except that the bottom will not be flat, for reasons to be described.

FIG. 2 shows a typicalimpact extruded container 14 of the kind preferably used in accordance with the invention as a starting member. The container 141 has a cylindrical side wall to and a bottom wall 118 joined to the side wall to at an edge portion 20. As best shown in FIG. 3, the edge portion 2a is thickened at the interior of the container and is in fact substantially thicker than either the side wall 16 or the bottom wall 18. The thickened portion is a peculiarity of impact extruded containers and results from the impact extrusion process in which a male die is forced at very high speed into a slugof aluminum or other suitable metal located in a female die. The impact causes the aluminum to flow over the male die, resulting in an impact extruded container (having a thickened bottom edge portion) which is then stripped away from the dies for use. Since the production of impact extruded containers is well known and has been carried out for many years, it will not be described in this application.

It will also be seen in FIG. 3 that the exterior of the edge portion 20 is curved in a sharp radius indicated at R1. This sharp radius is usual for cylindrical containers.

If the container 14 shown in FIG. 2 were tapered by drawing its material upwardly along the chain dotted line 22 shown in FIG. 2, this would result in a side wall 24 (FIG. 4) having a bump 25. The bump 25 is formed by the thickened portion 20 which. has been drawn into the side wall of the container but which cannot readily be smoothed by the drawing process. The problem results partly from the increased thickness of the bottom edge portion 20 and partly from the relatively sharp radius R1. The problem also results in substantial part from the setting of the metal molecules during the impact extrusion process, i.e., a crack or other discontinuity 25 would occur even if the radius R1 of the impact extruded container were relatively large and even if the bottom edge portion 20 were of uniform thickness. The existence of the bump 25 on the side wall of a finished container is highly undesirable visually and would interfere with printing or decorating the container. In general, such a discontinuity cannot be tolerated commercially.

According to the invention, the difficulty caused by the bottom edge portion 20 of the container i4 is eliminated by doming'the bottom of the container before tapering the container. As shown in FIG. 5, the bottom 18 of the container is forced upwardly to create a dome 26. The former position of the bottom 18 is shown in dotted lines in FIG. 5. It will be seen that because of the extra material required by the dome, the thickened edge portion 20 is displaced radially inwardly of the side wall 16 to occupy a new location indicated at 20' in FIG. 5. At the same time, a new edge portion 28 is formed connecting the bottom wall 18 with the side wall 16 of the container. The new edge portion 28 is formed from material which originally was located in the side wall 16, the side wall non having been shortened. Although the diameter of the container at the new edge portion 28 is the same as it was before the doming process, the radius R2 of the new edge portion 28 is typically substantially increased as compared with the radius R1 of the former edge portion 20.

The doming step shown in FIG. 5 is carried out in a conventional manner. Typically as shown in FIG. 6, male and female dies 30, 32 respectively are provided, having the appropriate dome contour, and the container. 14 is squeezed between them to cause the metal to flow to the desired contour. If necessary, a series of dies located at successive work stations may be used in succession to effect the doming of the container bottom.

After the bottom 18 of the container 14 has been domed, the container is then tapered. The tapering is accomplished in conventional manner by placing a tapered male die 34 (FIG. 7) having the final desired tapered shape inside the domed container 14, and then moving the container 14 and male die 34 past a series of work stations (not shown) each having a female die 36. Each female die 36 has a tapered interior surface 38. The male die 34 with the container 14 thereon is forced into each female die in turn to cause the material to flow to conform to the slope of the female die. The surface 38 at each work station is more tapered than that at the last work station, until finally at the last die 36a the interior surface 38a has the'final tapered shape desired.

The manner in which the container 14 changes shape as it is drawn in the female dies 36 is shown diagrammatically in FIG, 8. When the container 14 is forced into the first female die 36, the wall 16 becomes slightly tapered, as shown at 16a. Movement of the container 14 past further work stations results in further tapering of the side wall as shown at 16b, 16c. It will be seen that during the tapering process, the new edge portion 28 of the container 14 is forced upwardly to become part of the side wall. This causes no discontinuities in the side wall because the new ,edge portion 28v is of the same thickness as the remainder of the side wall and joins the original side wall 16 by a substantial radius R2 to provide a smooth flow path for the material. Most importantly, the new edge portion 28 is formed of material that was (in the original impact extruded container) flat (it was originally part of the container side wall), so that it does not have a difficult molecular set that would cause it to crack when it is drawn upwardly. Since the old edge portion 20' is located radially inwardly of the bottom edge of the final tapered side wall 160, the old edge portion 20' does not form part of the final side wall. Although the old edge portion 20' does represent an irregularity in the container, the irregularity is noticeable primarily inside the container and in any event is at the container bottom, where it will not cause difficulty.

ln the tapering process described with reference to FIGS. 7 and 8, the female die 36 is made sufficiently deep that the male die 34 with the container 14 thereon is forced only part way into the female die 36 and stops short of the bottom 40 of the die 36. In this way only the side wall 38 of the female die 36 acts on the container, thus achieving a smooth flow of the material at the bottom edge portion 28 of the container.

Although the use of male and female dies has been shown for doming the bottom of the container and then for tapering it, other methods can also be used. For example, as shown in H6. 9, the container can be inverted and placed on a carrier consisting of a support plate 42 with a support ring 44 fixed thereto. Since the open end of the container is held snugly by the support ring and plate, doming and tapering can be accomplished by moving the container on its supports through a series of work stations at which female dies of the appropriate contour are brought down on the container.

4 A typical die for doming the closed end of the container is indicated at 46 in H0. 9.

It should be noted that when the HO. 9 arrangement is used, only the portion 48 of the container adjacent the closed end will be tapered. The portion 50 adjacent the open end will continue to have a cylindrical wall. This partly tapered shape is useful for aerosol containers, in which the wall adjacent the open end should be cylindrical so that it can be necked and shaped to form a rim on which a valve can be seated.

If desired, and as shown in FIG. it) (where primed reference numerals indicate parts corresponding to those of H6. 8), the support ring 44 can be cylindrical instead of annular and can be located inside the open end of the container, where it again acts as a locator for the container.

it will be appreciated that the radially inward displacement of the old edge portion 20 to location 20' will vary depending on the amount of tapering desired, since for a small taper the old edge portion 20 need not be displaced as far inwardly as for a large taper. Typically for a twelve degree taper of an impact extruded container having an initial diameter of 1.75 inches, the old edge portion 20 is displaced radially inwardly by about 0.182 inches. This ensures that the surface to be drawn upwardly to form part of the new tapered side wall is composed entirely of a surface that is uniform in thickness and which was (in the original impact extruded container) entirely flat.

What I claim is:

l. A method of tapering a container having a first end, a cylindrical side wall, and an integral substantially flat end wall at the end of said container remote from said first end, said end wall being connected to said side wall at a first edge portion, comprising: doming said end wall towards said first end to form a domed end wall and thereby displacing said first edge portion radially inwardly so that said first edge portion forms part of said domed end wall, thereby shortening said side wall and forming a new edge portion joining said shortened side wall to said domed end wall, said new edge portion thus being formed from said cylindrical side wall; and then tapering said container by forcing the material at said new edge portion towards said first end to reduce the diameter of said container at said domed end wall.

2. A method according to claim I wherein said first edge portion has a curved exterior smoothly joining said side wall and said end wall, said curved exterior having a first radius of curvature; said new edge portion having a curved exterior also smoothly joining said side wall to said domed end wall, said curved exterior of said new edge portion having a second radius of curvature, said second radius of curvature being greater than said first radius of curvature.

3. A method according to claim 1 wherein said container is an impact extruded container and wherein said first edge portion is of thickness greater than that of said side wall and greater than that of said end wall.

4. A method according to claim 1 wherein said container is an impact extruded container and wherein said first edge portion is of thickness greater than that of said side wall and greater than that of said end wall and wherein the angle of said taper is between five degrees and twelve degrees relative to the axis of said container.

3,814,040 6 5. A method according to claim ll wherein said taperside wall of each female die contacts said container. ing is effected by forcing said container into a series of female dies each having a side wall having a progressively increasing taper, said container being forced into tamer an 'mpact extruded contamer" said female dies to a limited extent whereby only said 5 6. A method according to claim 1 wherein said con- 

1. A method of tapering a container having a first end, a cylindrical side wall, and an integral substantially flat end wall at the end of said container remote from said first end, said end wall being connected to said side wall at a first edge portion, comprising: doming said end wall towards said first end to form a domed end wall and thereby displacing said first edge portion radially inwardly so that said first edge portion forms part of said domed end wall, thereby shortening said side wall and forming a new edge portion joining said shortened side wall to said domed end wall, said new edge portion thus being formed from said cylindrical side wall; and then tapering said container by forcing the material at said new edge portion towards said first end to reduce the diameter of said container at said domed end wall.
 2. A method according to claim 1 wherein said first edge portion has a curved exterior smoothly joining said side wall and said end wall, said curved exterior having a first radius of curvature; said new edge portion having a curved exterior also smoothly joining said side wall to said domed end wall, said curved exterior of said new edge portion having a second radius of curvature, said second radius of curvature being greater than said first radius of curvature.
 3. A method according to claim 1 wherein said container is an impact extruded container and wherein said first edge portion is of thickness greater than that of said side wall and greater than that of said end wall.
 4. A method according to claim 1 wherein said container is an impact extruded container and wherein said first edge portion is of thickness greater than that of said side wall and greater than that of said end wall and wherein the angle of said taper is between five degrees and twelve degrees relative to the axis of said container.
 5. A method according to claim 1 wherein said tapering is effected by forcing said container into a series of female dies each having a side wall having a progressively increasing taper, said container being forced into said female dies to a limited extent whereby only said side wall of each female die contacts said container.
 6. A method according to claim 1 wherein said container is an impact extruded container. 